LU83518A1 - METAL CABLES FOR THE REINFORCEMENT OF ELASTOMERIC MANUFACTURED PRODUCTS - Google Patents

Description

DESCRIPTIVE MEMORY

FILED IN SUPPORT OF A REQUEST FOR

PATENT

"

FORMED BY

DÏÏNLOP LIMITKP for Wire ropes for the reinforcement of elastomeric manufactured products.

The present invention relates to a metallic cable for the reinforcement of elastomeric manufactured products, * for example tires.

The so-called "radial" tires, in particular those intended for heavy vehicles, generally comprise several plies of metal cords, under the tread, which together constitute a relatively inextensible reinforcement.

These cables usually include a core surrounded by one or more layers or helices of strands or elementary metal wires arranged so as to completely cover the core. The latter can itself be made of one or more metal wires, arranged in parallel or twisted together.

Experience has shown that tires made from such cords are seriously deficient when they come into contact with penetrating objects, such as nails, screws or sharp-edged stones, or after an accidental cut has been made. made in the> tread. The resulting defect allows the water which is encountered on the road and which could contain impurities or salts to penetrate to the cables of the external reinforcement ply and often even to one or more of the sub-plies. underlying.

A close examination of the used tires containing such cords, in particular at the time of retreading, shows that water or humidity tends to infiltrate between the various metallic wires of the cords by capillary action and to go up along these wires to their ends.

The steel of the cord (and / or the brass which generally covers the steel in a very thin layer) then undergoes a surface oxidation, so that the connection between the rubber mixture coating the cables and the metal disappears and that detachments premises take place and spread, which leads to removing the tire from service or making it necessary to carry out major repairs before retreading.

French patent n ° 2.001.7½ describes a metallic cable which comprises a core formed by a strand and an outer layer formed by strands which are relatively distant from each other, the space between the strands and the fact that a strand , in section, has a smaller section than that of a solid metal wire of the same outside diameter allows satisfactory penetration of the rubber during the coating of the cables. However, these cables have the disadvantage of being very expensive. For this reason, the strand of three metal wires has been replaced, for example, by single metal wires of larger diameter than that of each of the metal wires of the strand.

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Thus, strands comprising three metal wires with a diameter of 0.22 mm have been replaced by single metal wires with a diameter of 0.38 mm.

French Patent No. 1,264,878 describes an example of known cable which comprises a core formed by three elementary metal wires twisted together, in addition to an outer layer formed by elementary metal wires having a diameter such that they are not contiguous on the contour. of soul. English Patent No. 1,034,326 describes another cable in which the core is formed only of two elementary metal wires which are twisted together, while the outer layer or helix is formed of six elementary metal wires which are not not contiguous.

However, tires produced by means of such cords, although they are less expensive than tires produced with cords comprising strands in the outer layer, still have the aforementioned drawback of permitting the penetration of water by capillarity. The parallel elementary metal wires of the outer layer touch each other along lines or are very close to each other, while the strands, even when placed side by side, leave a gap in which the rubber can penetrate .

In addition, the cables corresponding to these last two aforementioned patents usually manifest inadequate mechanical characteristics or are too stiff, which makes them unacceptable for certain tires intended for vehicles with heavy loads.

The invention particularly aims to provide a construction of metal cords comprising an outer layer formed of elementary metal son which mitigates the drawbacks of known cords, but nevertheless ensures good penetration of the rubber.

Understanding the principle of the invention requires the introduction of the concept of "opening report".

The opening ratio, for metallic cables comprising a layer of elementary metallic wires, is determined in a plane perpendicular to the longitudinal axis of the cable and is defined for the purposes of the invention as being the ratio R between the distance e separating two elementary metal wires and the sum of the diameter D of the metal wires and this distance e. Therefore, we have:

According to the invention, a metallic cord for reinforcing elastomeric manufactured products * comprises a core having a longitudinal axis and a helix formed of elementary metallic wires wound parallel to each other around the core, the dimensions of the core , the number and the diameter of the elementary metal wires and their relative arrangement being such that the opening ratio of the elementary metal wires, as defined here, is at least 0.08.

According to the invention, it has been established that water or moisture cannot penetrate along the cables, for example after a tire has deteriorated, when the coating rubber penetrates perfectly into the cable and does not allow it to remain. no continuous channel between the constituent metal wires, this penetration of the rubber being obtained when the cords have an opening ratio of at least 0.08 and more advantageously from 0.1 to 0.25.

It is advantageous for the number of elementary metal wires in the propeller to be greater than or equal to seven, because the resulting cords then have a high breaking strength for a reasonable stiffness and an acceptable price.

The core can be formed of a strand or a rod, for example thermoret.ractable, having a suitable section and containing grooves, for example. The core may also have a multiple structure and may itself include a helix made of elementary metallic wires applied around a primary core, the helix then, most favorably, having an opening ratio of at least 0 , 08, in accordance with the invention.

According to a first embodiment of the invention, the cables have a structure n - ^ / 0- ^ + ïi ^ / ÇÎ ^.

The core is formed from n ^ elementary metal wires (n ^ being greater than or equal to 1) of the same diameter 0 ^, for example from 0.20 to 0.30 mm (advantageously 0.20 to 0.28 mm), twisted together with a pitch which may be, for example, from 8 to 16 mm, so as to form a strand. In certain constructions of the core, a metal wire of the same diameter or of smaller diameter is housed in the center and the metal wires of the core strand are wound on this central wire with an opening ratio of at least 0, 08. The helix or outer layer of the cable, arranged around the core, is formed of n ^ elementary metal wires of the same diameter 02¾ For example from 0.25 to 0.40 mm (advantageously 0.50 to 0.58 mm) wrapped together parallel to each other around the core with a pitch which can be, for example, from 12 to 22 mm. The number and the diameter of the elementary metal wires of the outer layer are such that the opening ratio is at least 0.08 and preferably from 0.1 to 0.25.

The direction of twist of the core metal wires and the direction of committing of the metal wires of the outer layer may be the same, the steps however being sufficiently different to ensure that the metal wires are in contact only at certain points. The senses can also be opposite, as specifically indicated in the examples below.

According to a second embodiment of the invention, the cables have a structure of the type nl ^ l + n2 ^ 2 above, but with periodic relaxation of the tension during the execution of the twist of the metal wires of the soul or the outer layer. In this way, the metal wires of the outer layer are not tightened around the core in places distant from the length of the cable. The penetration of the rubber is thereby improved.

* According to a third embodiment of the invention, the core of a cord of one of the above types is replaced by a cord or by a rod formed from a heat-shrinkable material, such as polyamide 6 or 6.6 called "Nylon", or polyester. When the core is made of a rod, it is advantageous that it has a rounded section and has, on the surface, grooves which cross the path of the elementary metal wires of the outer layer. During the vulcanization of a tire containing such cords as reinforcing elements, under high pressure and at high temperature, the withdrawal of the core of the cabled and its shortening favor the penetration of the coating mixture around the metallic wires of the outer layer and specifically at the ends, which always constitute a delicate point in a tire with a radial carcass.

According to a fourth embodiment of the invention, a cable comprises two successive layers of elementary metal wires surrounding the core or the preceding layer and comprising elementary metal wires whose number and diameter are such that each of the layers has a ratio opening of at least 0.08 and preferably 0.1 to 0.25.

In addition, a guipure thread sometimes called a "lace" can be applied around the cords which are the subject of the various embodiments of the invention.

The cables according to the invention have very valuable qualities for the manufacture of tires. Firstly, as already indicated, because of their high opening ratio, they allow good penetration of the coating mixture used for calendering the plies, specifically in the case of tires intended for heavy vehicles. It is known that these mixtures have a high viscosity. In addition, cables which contain elementary metal wires in the outer layer have good compactness. This characteristic is very important, because for an equal mechanical resistance, the thickness of the layers formed is reduced.

The space between the metallic wires of the cables in accordance with the invention and the penetration of the rubber between these metallic wires attenuates the stiffness and eliminates practically all the breaks in the cables due to friction between the elementary wires. This defect is known in the art under the name of "bite".

The cables according to the invention also have good axial stability, especially when the direction of twist of the core and the direction of committing of the metal wires in the propeller or the outer layer are opposite. This axial stability is accompanied by good stability of the core when the cord is subjected to deformations and also good properties of resistance in traction and compression. In addition, when using plies reinforced by means of the cords according to the invention for the manufacture of tires, the cutting of the plies is clean and does not lead to any deformation.

The cables in accordance with the invention can be used in very large tires intended to support very heavy loads and especially in tires for vehicles with heavy loads.

Other properties and advantages of the invention will emerge from the description which is given below, by way of example only, with reference to the appended drawings, in which:

Fig. 1 is a sectional view of a known cable comprising an outer layer formed of strands;

Fig. 2 is a sectional view of a known cable, the outer layer of which, formed of elementary metallic wires, does not allow proper penetration of the rubber, and

Fig. 3 to 8 are sectional views of different embodiments of cables in accordance with the invention.

The cable 10 of FIG. 1 having the structure 1x4 / 0.22 + 6x4 / 0.22 + 1 / 0.15, generally used for many years for the manufacture of tires, comprises seven strands 11, each of which comprises four metallic wires 12 of a diameter of 0.22 mm, and is wrapped in a guipure wire 13 with a diameter of 0.15 mm. The core is formed by one of the strands 11 with four wires (diameter of 0.22 mm) and the outer layer is formed by the six remaining strands. This cable has very good mechanical properties, but its price is high.

Fig. 2 is a sectional view of a cord 20 of structure 1x3 / 0.20 + 6 / 0.38, currently used in the tire industry, which comprises a core formed by a strand 21 made of three wires 22, each with a diameter of 0.20 mm, and an outer layer formed by six elementary metal wires 23, each with a diameter of 0.38 mm. Experience has shown that this cable does not allow good penetration of the rubber and its opening ratio as defined here is much lower than the lower limit of the opening ratio of cables in accordance with the invention.

Fig. 3 is a sectional view of a first embodiment of a cable 30 according to the invention.

The cable 30 has a structure 4 / 0.20 + 7 / 0.30, that is to say that it comprises a central core strand 31 made of four metal wires 32 with a diameter of 0.20 mm and seven elementary metal wires 33 forming a helix and having a diameter of 0.30 mm.

Fig. 3 also shows how the opening report is evaluated. The space _e is the distance separating two adjacent elementary metal wires 33 in the propeller, these wires each having the diameter D. The opening ratio R is equal to the ratio between the space £ and the sum of the space e and of the diameter ¢. The cable 30 of FIG. 3 has an opening ratio of 0.117 and experience has shown that this value allows good penetration of a high viscosity mixture which is used to calender the plies of tires for heavy vehicles.

Fig. 4 is a sectional view of a second embodiment of a cable 40 according to the invention, derived from the cable 30 illustrated in FIG. 3- The cable 40 has a structure 1 / 0.12 + 4 / 0.20 + 7 / 0.30, that is to say that it comprises a metal wire 41 with a diameter of 0.12 mm forming a primary core surrounded by four metal wires 42 with a diameter of 0.20 mm, this constituting the core. The opening ratio R of the outer layer comprising the four metallic wires 42 of the core is equal to 0.13. Around the core, seven elementary metal wires 43 with a diameter of 0.30 mm form a helix, the opening ratio of which is 0.176. The central metal wire 41 constituting the primary core therefore ensures the spacing between the metal wires 42 of the strand by comparison with the embodiment of FIG. 3 and household, therefore, a larger space between the metal son 43 of the outer layer.

Fig. 5 is a sectional view of a third embodiment of a cable 50 according to the invention.

Cable 50 has a structure (1 + 6) / 0.25 + 8 / 0.35? that is, it has a core made of seven metal wires 51 with a diameter of 0.25 mm and an outer layer formed by eight elementary metal wires 52 with a diameter of 0.35 mm twisted around the soul. The opening ratio of this cable is 0.169.

Fig. 6 is a sectional view of a fourth embodiment of a cable 60 according to the invention having a structure 1x3 / 0.20 + 6 / 0.38, that is to say

Me at the end of Fig. 2. However, for the manufacture of the cord 60 according to the invention, the elementary metal wires 61 of the outer layer undergo periodic relaxations, so that they are not tightened on the core 62 and remain separated from it. this. Therefore, in FIG. 6, the outer metal wires 6l are separated from the core 62 by a distance x of 0.1 mm. Therefore, the opening ratio reaches a value of 0.248 and the penetration of the rubber is excellent.

Fig. 7 is a sectional view of a fifth embodiment of a cable 70 according to the invention.

The cord 70 comprises a core 71 which is formed of Nylon 6.6, which has an outside diameter of 0.6 mm and which has six helical grooves 72 with a depth of 0.1 mm formed in its peripheral surface. Eight metal wires 73 with a diameter of 0.30 mm are wound on the core 71. With an opening ratio R of the metal wires 73 is 0.13. The penetration of the rubber is facilitated by the grooves 72 of the core 71 and by the withdrawal which takes place during the vulcanization of a tire containing cords whose core is of this kind. This withdrawal, which reaches only the core 71> causes a separation between the external metal wires 73 ·

Fig. 8 is a sectional view of a sixth embodiment of a cable 80 according to the invention having very high mechanical strength. Cable 80 is designed for very large tires used, for example, not paired on tractors or trailers and has the structure 4 / 0.23 + 7 / 0s35 + 11 / 0.38. A core formed of a strand 8l constituted by four metal wires 82 with a diameter of 0.25 mm is surrounded by a first layer of seven metal wires 83 with a diameter of 0.35 mm, having a ratio of opening R of 0.15 * f, and a second layer of eleven metal wires 84 with a diameter of 0.38 mm, having an opening ratio R of 0.20, around the first layer. The pitch of the intermediate layer is opposite to that of the core and that of the outer layer.

The table below makes it possible to compare the characteristics and properties of various known cables (examples 1 and 2) and cables in accordance with the invention (examples 3 to 10).

In this table, the structure is indicated as specified above. The construction indicates the pitch of twisting or commetting, as well as its direction (S or Z).

The opening ratio is as defined above. The breaking strength is measured with a dynamometer. The stiffness can be measured using a "Haber" device manufactured by the Company Instrument Corporation (United States of America), the values being a torque expressed in (10 ^ U.m.).

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Claims (12)

1. Wire rope for the reinforcement of elastomeric manufactured products comprising a core having a longitudinal axis and a helix formed of elementary metal wires wound parallel to each other around the core, characterized in that the dimensions of the core (31 , 41,42,51,62,71,81), the number and the diameter of the elementary metallic wires (33,43,52,61,73,84) and their relative arrangement are such that the opening ratio (R ) elementary metal wires (33,43,52,61,73,84), as defined here, is at least 0.08. 2, - Wired according to claim 1, characterized in that the opening ratio (R) is 0.1 to 0.25 · 3 · - Wired according to claim 1 or 2, characterized in that the propeller comprises at least seven elementary metal son (33,43,52,73,84). 4.- Wired according to any one of the preceding claims, characterized in that the core is formed by a strand (31,41,42,51,62,82). 5 · - Wired according to any one of claims 1 to 3, characterized in that the core contains elementary metal wires (42) of the same diameter twisted together around a central metal wire (41) of equal or more diameter small, the external elementary metal wires (42) of the core having an opening ratio, as defined here, of at least '0.08. 6.- Wired according to any one of the preceding claims, characterized in that the metal wires forming the core have a diameter of 0.20 to 0.28 mm and a pitch of 8 to 16 mm. 7 · - Wired according to any one of the preceding claims, characterized in that the metallic wires forming the helix have a diameter of 0.50 to 0.58 mm and are applied with a committing pitch of 12 to 22 mm. 8.- Câhlé according to any one of the preceding claims, characterized in that the direction of twist of the metallic wires of the core is opposite to the direction of committing the metallic wires of the propeller. 9 · - Câhlé according to any one of the preceding claims, characterized in that the elementary metal wires (61) of the propeller are away from the core '(62). P 10. Câhlé according to any one of the preceding claims, characterized in that the core (81) is surrounded by a first layer of elementary metal wires (85) wound parallel to each other, then by the propeller (84) , the number and the diameter of the metal wires of the first layer (85) and of the propeller (84) being such that the opening ratio (R) of each, as defined here, is greater than 0.08. 11. Cable according to any one of claims 1 to 5, characterized in that the core (71) is formed of a rod of heat-shrinkable material. 12. Cable according to claim 6, characterized in that the core (71) carries in its peripheral surface grooves (72). t *